1. Field
The present disclosure relates to an apparatus for attaching two substrates to each other, and more particularly, to an apparatus for attaching substrates which is provided with a buffering member between an upper chamber and a lower chamber.
2. Background
Recently, with development of an information society, there have been increased requirements for display devices. Therefore many different types of display devices have been developed, such as a liquid crystal display (LCD), plasma display panel (PDP), etc. Users of these display devices require superior video quality, light weight as well as large size. Therefore, there has been recently developed a super large size LCD having a size of more than 50 inches.
An LCD display is a display device which displays information on its screen using anisotropy of a refractive index of a liquid crystal. The LCD display is manufactured by adding liquid crystals between two substrates and attaching the two substrates to each other. One of the two substrates is a driving device array substrate and the other is a color filter (CF) substrate. A plurality of pixels are formed on the driving device array substrate and each pixel is formed with a driving device such as a thin film transistor (TFT). A color filter layer for realizing color is formed on the color filter substrate, along with pixel electrodes, a common electrode and an alignment film for aligning liquid crystal molecules.
In a process of manufacturing such a display device, the process of attaching the two substrates to one another is very important. As the size of the display devices has increased, the size of the apparatus for attaching the two substrates has also increased.
The substrate attaching apparatus is designed to create a sealed attachment space. During the attachment process, this space is evacuated to create a vacuum. As the substrate attaching apparatus becomes larger, a load applied to the attaching apparatus due to a pressure difference between an inside and an outside of the attaching chamber has also increased. This load acts on the walls of the chamber body and can cause a deformation of the chamber. The deformation forces can also apply an excessive force to a lifting device for lifting one half of the chamber.
The lifting device of the attaching apparatus is provided with a lifting motor which provides a driving force for lifting the chamber. Lifting screws rotate axially to lift and lower a frame for supporting a portion of the chamber. Typically, the lifting device lifts a lower chamber until it is coupled with an upper chamber to seal the attachment space. The chamber is then vacuum exhausted. The vacuum state within the attachment space causes the lower chamber to be pulled up by a pressure difference. When the lower chamber is pulled up, forces are applied to the frame, the lifting screws, etc. which support the chamber. Therefore, the frame, the lifting screws, and other portions of the lifting apparatus may be deformed. This, in turn, tends to result in frequent replacement of parts and a short lifetime of the substrate attaching apparatus.
Also, during the attaching process, it is important to adjust a gap between the substrates so that the substrates have a uniform gap between them, and to also align the relative positions of the substrates so that both substrates are attached to each other at the exact desired positions. This gap adjustment process and the position alignment process can be accurately performed only after the lower chamber has been raised and fixed to the upper chamber.
Because, the attaching apparatus becomes larger with an enlargement of the substrate size, the weight of the lower chamber and the substrate placed within the lower chamber becomes heavier when the display size increases. Therefore, a load applied to the lifting part which lifts and supports the lower chamber also increases. The heavier loads of the larger attaching apparatus can cause the lifting screw to be elastically deformed. As a result, an error may occur in the gap adjustment process or the position alignment process.